Retention & relapse /certified fixed orthodontic courses by Indian dental academy

RETENTION AND RELAPSE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


After malposed teeth have been moved into the
desired position they must be mechanically
supported until all tissues involved in their support
and maintenance of their new positions shall have
become thoroughly modified, both in structure and
in function, to meet the new requirements”
“

Angle (1907)


CONTENTS
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INTRODUCTION
SCHOOLS OF THOUGHT FOR RETENTION
SEMANTICS OF POST ORTHODONTIC TREATMENT CHANGES
THEOREMS OF RETENTION
FACTORS INFLUENCING RETENTION AND STABILITY
FACTORS THAT MODIFY THE RETNTION PROTOCOL
CAUSATIVE FACTORS FOR RELAPSE
RETENTION AFTER CLASS II CORRECTION
CLASS III CORRECTION
DEEP BITE CORRECTION
ANTERIOR OPENBITE CORRECTION

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LONG TERM RETENTION STUDIES
RETENTION PLANNING
TIMING OF RETENTION
RETENTION APPLIANCES
RECOVERY AFTER RELAPSE
CONCLUSION

INTRODUCTION
Orthodontists have long since been aware of the fact that
teeth that have been moved in or through bone by
mechanical appliances have a tendency to return to their
former positions. It is the purpose of Retention to
counteract this tendency. Although it has been stated that
correct diagnosis and planning of treatment, followed by a
careful stabilizing of the final result, would minimize the
importance of retention, Relapse tendencies still exist in a
fairly high percentage of cases treated. Our ability to
achieve long term Stability and our understanding of the
factors underlying stability may be the least well founded in
this ‘triad’, clear indication being our need for retention of
achieved results – at times long term retention.

DIFFERENT SCHOOLS OF THOUGHT FOR RETENTION
THE OCCLUSION SCHOOL
Kingsley (1880) stated, “The occlusion of the teeth is the most potent factor
in determining the stability in a new position”.
THE APICAL BASE SCHOOL
In the middle 1920s a second school of thought formed around the writings
of Axel Lundstrom (1925), who suggested that the apical base was one of the
most important factors in the correction of malocclusion and maintenance of
a correct occlusion. McCauley (1944) suggested that intercanine width and
intermolar width should be maintained as originally presented to minimize
retention problems. Strang (1958) further enforced and substantiated this
theory. Nance (1947) noted, “Arch length may be permanently increased only
to a limited extent.”


THE MANDIBULAR INCISAL SCHOOL
Grieve (1944) and Tweed (1952) suggested that the mandibular incisors
must be kept upright and over basal bone.

THE MUSCULATURE SCHOOL
Rogers (1922) introduced a consideration of the necessity of establishing
proper functional muscle balance.


SEMANTICS OF POSTORTHODONTIC TREATMENT CHANGES
[Semantics: the study of language meaning]

RETENTION
Moyers (1973) defined retention as “the holding of teeth following orthodontic
treatment in the treated position for the period of time necessary for the
maintenance of the result.”
Joondeph and Riedel (1985) explain retention as “the holding of teeth in ideal
aesthetic and functional positions.” Retention is accomplished by a variety of
mechanical appliances.


RELAPSE
Robert Moyers states that relapse is the term applied to the loss of any
correction achieved by orthodontic treatment.
Horowitz and Hixon (1969) defined relapse in general as “changes in tooth
position after orthodontic treatment”.
Enlow (1980) defined relapse as “a histogenetic and morphogenic
response to some anatomical and functional violation of an existing state
of anatomic and functional balance.” It is usually thought of as a
“rebound” movement in which teeth recoil back somewhere close to their
original positions once retentive forces are moved.
STABILITY
Stability is the condition of maintaining equilibrium. This refers to the
quality or condition of being stable; the fixity of position in space or the
capacity for resistance to displacement.

PHYSIOLOGIC RECOVERY
Horowitz and Hixon (1969) explain physiologic recovery as the change to
the original physiologic state after completing treatment.
DEVELOPMENTAL CHANGES
Developmental changes are those which occur irrespective of whether
orthodontic treatment was implemented or not. These changes could
easily be overlooked when assessing post treatment relapse.
POSTRETENTION SETTLING
Settling can be described as the establishment of a desired position, the
act of ceasing to move or “settling down” and maintaining a correctly
balanced position. This term thus indicates the post treatment changing
process versus a term such as metaposition, which refers to the
meticulously planned changes after the removal of the orthodontic
appliances.

METAPOSITION
Metaposition denotes the desirable and expected post treatment changes
that are anticipated (Ricketts, 1993). These changes are not relapse and
must be part of the treatment itself.

RECIDIEF
The term “recidief” has been used to describe changes that occur from the
end of treatment back to the original situation (Dermaut, 1974).


WHY IS RETENTION NECESSARY?

The proposed basis for holding the teeth in their treated position
is to:
1) Allow for periodontal and gingival reorganization;
2) To minimize changes from growth;
3) To permit neuromuscular adaptation to the corrected tooth position;
and
4) To maintain unstable tooth position, if such positioning is required for
reasons of compromise or esthetics.


BASIC THEOREMS FOR RETENTION
Richard A Riedel (AO 1960) had discussed a number of possible
explanations of Retention and Relapse.
THEOREM 1: Teeth that have been moved tend to return to their former
positions.
THEOREM 2: Elimination of the cause of malocclusion will prevent
recurrence.
THEOREM 3: Malocclusion should be overcorrected as a safety factor.
THEOREM 4: Proper occlusion is a potent factor in holding teeth in their
corrected positions.
THEOREM 5: Bone and adjacent tissues must be allowed to reorganize
around newly positioned teeth.


THEOREM 6: If lower incisors are placed upright over basal bone, they
are more likely to remain in good alignment.
THEOREM 7: Corrections carried out during periods of growth are less
likely to relapse.
THEOREM 8: The farther teeth have been moved, the less likelihood of
relapse.
THEOREM 9: Arch form, particularly in the mandibular arch, cannot be
permanently altered by appliance therapy.
To Riedel’s theorems might be added the following:
THEOREM 10: Many treated malocclusions require permanent retaining
devices.
This is less true for cases treated to meticulous occlusal
goals and with respect for the dynamics of growth and occlusal function……
Robert E Moyers (1970).


FACTORS INFLUENCING RETENTION AND
STABILITY


Factors that affect post treatment stability include……..
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Alteration of arch form

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Periodontal and gingival tissues

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Mandibular incisor dimensions

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Influence of environmental factors and neuromusculature

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Consideration of continuing growth

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Post treatment tooth positioning and establishment of functional occlusion

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Role of developing third molars

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Influence of the elements of the original malocclusion


ALTERATION OF ARCH FORM
It is generally agreed that arch form and width should be maintained during
orthodontic treatment. In certain cases, where arch development has occurred under
adverse environmental conditions, arch expansion as a treatment goal may be tolerated.
Mills (Br Dent J 1966) found stability after proclination in cases with skeletal
deep bites and retroclined incisors in conjunction with a digit or lip entrapment habit.
Årtun (AO 1990) stated that proclination may be successful provided that the
lower incisors are initially retroclined, a reason for the retroclination determined, and
the cause eliminated during treatment. Evidence shows that intercanine and intermolar
widths decrease during the postretention period, especially if expanded during
treatment. For this reason, the maintenance of arch form rather than arch development
is generally recommended.
…………………

Little et al (AJO 1981) maintained that intercanine and intermolar
width will relapse if expanded in Class II Division 2 cases as much as in
other Angle classifications. In cases of mandibular expansion concurrent
with Rapid Palatal Expansion Haas(AO 1980) and Sandstrom et al.(AJO
1988) found that maintenance of 3 to 4 mm intercanine width and up to 6
mm intermolar width was possible when expansion was carried out
concurrently with maxillary apical base expansion
De La Cruz et al. (AJO 1995) carried out a 10 year postretention
study on 87 patients to determine the long-term stability of orthodontically
induced changes in maxillary and mandibular arch form. The results
showed that although there was considerable individual variability, arch
form tended to return toward the pretreatment shape. They concluded that
the patient's pretreatment arch form appeared to be the best guide to future
stability.


PERIODONTAL AND GINGIVAL TISSUES
Orthodontic movement to correct tooth rotations is proposed to result in
stretching of the collagen fibers. The PDL reorganization is important for
stability because of the periodontal contribution to the equilibrium that normally
controls tooth position. Within 4 to 6 months, the collagenous fiber networks
within the gingiva have normally completed their reorganization, but the elastic
supracrestal fibers remodel extremely slowly and can still exert forces capable of
displacing a tooth at one year after removal of an orthodontic appliance.
Brain(AJO 1969) and Edwards(AJO 1970) advocated gingival fiber
surgery (Circumferential Supracrestal Fiberotomy) to allow for the release of soft
tissue tension and reattachment of the fibers in a passive orientation after
orthodontic tooth rotation. In 1971 a prospective study was initiated by Edwards
with 160 patients up to 14 years post treatment. The results were published in
1988 (AJO 1988) and show a significant difference in the irregularity index
between the control and treatment groups at both 6 and 14 years post treatment.
No significant loss of attachment or other periodontal abnormalities were
reported

MANDIBULAR INCISOR DIMENSIONS
The notion that mandibular incisor dimensions were correlated
with lower incisor crowding was reintroduced by Peck and Peck (AO 1972)
after a study of 45 untreated normal occlusions. They advocated reduction
of mandibular incisors to a given faciolingual/mesiodistal ratio to increase
stability. Peck and Peck's work, however, was criticized since their
recommendations were based on a study involving untreated rather than
treated cases. Young patients with ideal lower incisor alignment were
used in the study. It is possible that these cases would show crowding if
followed long term.
To evaluate whether the Peck and Peck ratio had long-term value,
Gilmore and Little (AJO 1984) studied 134 treated and 30 control cases a
minimum of 10 years postretention. They showed a weak association
between long-term irregularity and either incisor width or the
faciolingual/mesiodistal ratio.

INFLUENCE OF ENVIORNMENTAL FACTORS AND
NEUROMUSCULATURE
Strang(AO 1959) theorized that the mandibular intercanine and
intermolar arch widths are accurate indicators of the individual's muscle balance
and dictate the limits of arch expansion during treatment.
Weinstein et al. and Mills (Br Dent J 1966) stated that the lower incisors
lie in a narrow zone of stability in equilibrium between opposing muscular
pressure, and that the labiolingual position of the incisors should be accepted and
not altered by orthodontic treatment. Reitan(AJO 1969) claimed that teeth tipped
either labially or lingually during treatment are more likely to relapse.

The initial position of the lower incisors has been shown to provide the best guide
to the position of stability in two separate studies (Little et al. AJO 1985 &
Houston et al. EJO 1990). In over 50% of cases the lower incisors ultimately
stabilized at a point between the pretreatment and post treatment positions.
These results indicate that if lower incisor advancement is a treatment objective,
permanent retention is essential for maintenance of the result .

CONSIDERATION OF CONTINUING GROWTH
Litowitz (AO 1948) stated that cases exhibiting greatest amount of
growth during treatment showed less relapse. Riedel (AO 1960) reflected on the
fact that growth may aid in the correction of orthodontic problems but may also
cause relapse of treated cases. Nanda and Nanda (AJO 1992) agree with this and
maintain that any skeletal changes that occur during retention may attenuate,
exaggerate, or maintain the dentoskeletal relationship.
Facial development may result in secondary crowding especially in
extreme growth patterns such as forward mandibular growth rotation where
increased lingual movement of lower incisors may be seen. Others have stated
that growth is not a major influence in development of mandibular anterior
irregularity, (Sinclair & Little AJO 1985) and this is likely the case in an average
grower.
Nanda and Nanda(AJO 1992) found that the pubertal growth spurt for
patients with skeletal deep bite occurs on average 1.5 to 2 years later than is the
case for open bite cases. For this reason, a longer retention period for the
skeletal deep bite patients is advocated to counteract the continuing effect of
dentofacial growth after the completion of orthodontic treatment.

POSTTREATMENT TOOTH POSITIONING AND ESTABLISHMENT
OF FUNCTIONAL OCCLUSION

Adequate interincisal contact angle may prevent overbite relapse and
good posterior intercuspation prevents relapse of both crossbite and AP
correction. Less relapse of mesiodistal movement occurs in the absence of
occlusal stress. A perfect molar relationship was found to be a significant factor
in maxillary incisor alignment in a study of 226 postretention cases, (Schwarze
CW BJO 1995) and a RCP - ICP slide was found to have a statistically significant,
though clinically only moderate, influence on mandibular incisor irregularity
postretention (Weiland FJ EJO 1994).


ROLE OF DEVELOPING THIRD MOLARS
The role of third molars in lower incisor crowding has been debated
for more than a century. One theory commonly reported is that of the third
molars creating space to erupt by causing anterior teeth to crowd.
Woodside (JCO 1970) postulated that in the absence of third molars,
the dentition could settle distally in response to forces generated by growth
changes or soft tissue pressures. This implies a passive role of the third
molars in the development of late crowding by hindering that adjustment.
Recent studies show a statistically significant but not a clinically significant
role of third molars in postretention crowding.
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Broadbent(AO 1941) was an early advocate of the insignificant role
played by third molars in late lower incisor crowding. Several studies show a
reduction in arch length and an increase in crowding with age. However, no
difference in incisor crowding could be found in groups with impacted,
erupted, missing, or extracted wisdom teeth.
Richardson(AO 1982) demonstrated a significant forward movement
of first molars between the ages of 13 and 17 years. This was correlated with the
increase in lower arch crowding that occurred during the same period.
Ades et al. (AJO 1990) compared four groups of patients who were a
minimum of 10 years out of retention. They found no difference in mandibular
incisor crowding, arch length, intercanine width, and eruption patterns of
mandibular incisors and molars between the groups.
In summary, all of the conflicting data regarding third molars tends to indicate
that if third molars were a contributing factor in the development of late lower
incisor crowding, their role is likely to be one of minor importance.

INFLUENCE OF THE ELEMENTS OF THE ORIGINAL
MALOCCLUSION
Overbite increase postretention is related to the amount reduced
during treatment, although generally 30% to 50% of the correction is retained.
It is suggested that overbite relapse tends to occur in the first 2 years
posttreatment and maintenance of intercanine width is thought to increase
stability. Most studies do not support a greater relapse in Class II Division 1
cases when compared with other malocclusion groups, however, a slight
change in overjet toward pretreatment values was demonstrated in all
malocclusion groups.
When teeth are aligned by orthodontic treatment, there is a
documented tendency for a return toward the original pattern of malocclusion
(Kalplan AJO 1966). For this reason, rotational overcorrection has been
advocated.
Little et al. (AJO 1981) however, noted that there are many exceptions to this
rule with greater than 50% of the rotations or displacements relapsing in an
opposite direction.

ROLE OF TRANSVERSE DISCREPENCIES
There is inevitably a tendency for relapse associated with Rapid
Palatal Expansion techniques. Typically the clinician must significantly
overcorrect in the transverse dimension, anticipating that a more normal
relationship will occur during the relapse stages. Additionally the expansion
appliance must be maintained passively or removable appliance placed to aid
in transverse retention.

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Storey (AJO 1973) has documented experimentally that rapid
expansion results in a predominantly destructive process in which the sutural
connective tissue becomes disruptive and edematous. This is followed by
eventual filling of immature bone as a healing response. The growing of bone
of sufficient maturity requires a slow steady rate of formation with lateral
separation of bones on the order of 0.5 to 1mm per week. Results of Storey’s
experiments show that slow separation with continued growth of bony
serrations within the suture provides the best retention with the least potential
for relapse.
Castro, Cotton, and Hicks (University of Washington, AJO 1973, 1979)
have further evaluated experimentally and clinically the stability of palatal
expansion with light continuous forces and have concluded that this technique
is more stable than rapid expansion.
………………..

Anatomically, the limitation of palatal expansion is not the fusion of
the midpalatal suture but rather changes in morphology of suture caused by
maturation. As the patient ages, further intercuspation and interdigitation of
bony serrations take place until the suture becomes mechanically difficult to
expand at older ages. These changes may occur as early as 13 to 14 years.
Early expansion with light forces, achieved before these maturation changes
will allow maximal skeletal separation, with normal physiological bone
deposition enhancing the long term stability in this plane of space.


GENDER AND SEX DIFFERENCES
Growth is an aid in the correction of many types of orthodontic
problems, but it also may cause relapse in treated orthodontic patients.
Orthodontists take advantage of growth when treating patients in the
transitional dentition period with headgear anchorage or functional
appliances. With cervical traction the normal forward movement of the
maxillary molars seems to be restrained while the mandible continues in its
course of growth, and a normal tooth relationship may eventually be reached
(Harris J AJO 1962, Lagerström AO 1967).
The forward translation of the mandibular denture on its base after
the use of class II elastics or functional appliances is generally regarded as
being undesirable, for apparently the mandibular posterior teeth do not
migrate distally again. Mandibular anterior teeth in their attempt to upright to
their former positions, frequently break contact and crowd to the lingual.

PRINCIPLES OF RETENTION AGAINST INTRA-ARCH
INSTABILITY:
Comparing the position of the teeth at the conclusion of treatment with
their original positions can identify the direction of potential relapse .
[Teeth will tend to move back in the direction from which they came,
primarily because of elastic recoil of gingival fibers but also because of
unbalanced tongue-lip forces.]
Teeth require essentially full-time retention after comprehensive
orthodontic treatment for the first 3 to 4 months after a fixed orthodontic
appliance is removed.
[To promote reorganization of the PDL,
however, the teeth should be free to flex individually during mastication, as
the alveolar bone bends in response to heavy occlusal loads during
mastication. This requirement can be met by a removable appliance worn
full-time except during meals or by a fixed retainer that is not too rigid.]

Because of the slow response of the gingival fibers, retention should be
continued for at least 12 months if the teeth were quite irregular initially but can
be reduced to part-time after 3 to 4 months. After approximately 12 months it
should be possible to discontinue retention in non-growing patients. Some
patients who are not growing will require permanent retention to maintain the
teeth in what would otherwise be unstable positions because of lip, cheek, and
tongue pressures that are too large for active stabilization to balance out.
Patients who will continue to grow, however, usually need retention until
growth has reduced to the low levels that characterize adult life.


OCCLUSAL AND OTHER FACTORS WHICH MAY MODIFY THE
RETENTION PROTOCOL
Comprehensive orthodontic treatment is usually carried out in the early
permanent dentition, and the duration is typically between 18 and 30 months.
This means that active orthodontic treatment is likely to conclude at age 14 to
15, while anteroposterior and particularly vertical growth often do not subside
even to the adult level until several years later. Long-term studies of adults
have shown that very slow growth typically continues throughout adult life,
and the same pattern that led to malocclusion in the first place can contribute
to deterioration in occlusal relationships many years after orthodontic
treatment is completed.


The various factors include…….
-Lower Incisor alignment
-Corrected Rotations of anterior teeth
-Changes in the anteroposterior lower incisor position
-Correction of Deep Overbite
-Correction of Anterior Open Bites
-Patients with a history of periodontal disease or root resorption
-Growth Modification treatment
-Correction of Posterior and anterior Crossbites
-Adult Patients
-Spaced Dentitions


Lower incisor alignment:
Increases in lower incisor irregularity occur throughout life in a large
proportion of patients following orthodontic treatment and also in untreated
subjects. Recent evidence suggests that most change will take place by the
middle of the third decade (Richardson ME EJO 1998). It has been
suggested that prolonged retention of the lower labial segment until the end
of facial growth may reduce the severity of lower incisor crowding (Sadowsky
C AJO 1994).
Patient’s expectations of the stability of their lower incisor alignment
should be considered on completion of orthodontic treatment. If an
individual is unwilling to accept any deterioration in lower incisor alignment
following orthodontic treatment then permanent fixed or removable retention
may have to be considered


Corrected rotations of anterior teeth:
As the supracrestal gingival fibres are known to take the longest
amount of time to reorganise, prolonged retention of corrected rotations may
be helpful in reducing relapse. While the use of adjunctive circumferential
supracrestal fiberotomy has been shown to be effective in reducing relapse
within the first 4-6 years after debonding, the additional long term clinical
benefit from the procedure is relatively small (Edwards JG AJO 1988).
Changes in the antero-posterior lower incisor position:
Any intentional or non-intentional change of more than 2mm indicates
the need for long-term or indefinite retention (Proffit).


Correction of deep overbite:
Following the correction of a very deep overbite, the use of an anterior
biteplane until the completion of facial growth has been recommended. This
may be particularly useful when there is evidence of an anterior mandibular
growth rotation. (Proffit, Burstone & Nanda)

Correction of anterior open bites:
While the use of retainers incorporating posterior biteblocks has been
recommended for prolonged retention of anterior open bite malocclusions with
unfavourable growth patterns, there is currently a lack of scientific evidence to
support this. (Proffit)


Patients with a history of periodontal disease or root resorption:
In patients with previously treated severe periodontal disease,
permanent retention is advised. For those with minimum to moderate disease,
a more routine retention protocol can be used (Zachrisson) . There is evidence
of an increased risk of deterioration of lower incisor alignment post-retention
in cases with root resorption or crestal bone loss (Sharpe W AJO 1987). These
cases may therefore benefit from prolonged retention.
Growth modification treatment:
Following the use of headgear or functional appliances, retention
using a modified activator appliance has been reported as effective in
maintaining Class II correction (Weislander L AJO 1993).


Correction of posterior and anterior crossbites:
When the incisor overbite and posterior intercuspation are adequate
for maintaining the correction, no retention is necessary (Kaplan AJO 1988).
Adult Patients:
When the periodontal supporting tissues are normal and no occlusal
settling is required, there is no evidence to support any changes in retention
protocol for adult patients compared with adolescent patients.
Spaced dentitions
Permanent retention has been recommended following
orthodontic treatment to close generalised spacing or a midline diastema in
an otherwise normal occlusion (Graber & Vanarsdall).

CAUSATIVE FACTORS FOR RELAPSE
Most of the causative factors may be related to,
-Craniofacial growth
-Dental development &
-Muscle function

CRANIOFACIAL GROWTH
-Bjork (1968) showed the high variability of normal facial growth in
one of his first studies describing the use of metal implants in
cephalometrics. Late growth changes may be responsible for
posttreatment relapse, especially after correction of class III malocclusion.
-Growth and changes in muscles and surrounding soft tissue
structures are relatively well synchronized with the growth of the skeletal
framework. The craniofacial complex is regarded as a structure with
specific functions, classified as functional cranial components, and
consisting of a functional matrix and a skeletal unit, which protects and
supports this matrix. It has been shown that parts of the functional matrix
have a direct influence on the bone during orthodontic treatment.
.......................


-Relapse of the overjet and overbite has been observed and has been
mainly due to changes in incisor inclination. The tendency to relapse is slightly
greater in class II division 2 cases than in class II division 1 cases. As the
maxillary growth is completed on average 2 to 3 years before mandibular
growth, dentoalveolar structures may have difficulties in compensating for this
discrepancy, which may result in an increased overbite.

-Bjork (1972) and Sakuda (1976) showed that the dentoalveolar
structures may be influenced by the facial morphology. Permanent teeth in low
angle cases should have a more anteriorly directed path of eruption than in
normal individuals, which, together with a deep bite, might unfavourably
influence the stability in the lower anterior region. Mandibular incisor crowding
is also believed to be related to anterior (upward) rotation of the mandible.


DEVELOPMENT OF THE DENTITION
Continuous eruption of teeth→ The physiologic changes of the
dentition from early childhood into adolescence, and from young adulthood
into adulthood are gradual process. A slight continuous eruption of teeth has
been observed even after the establishment of occlusion post adolescence.
Arch length changes→ The arches reduce sagittally until the age of 14
years and even later. Crowding of the lower incisors quite commonly develops
in modern man and coincides with this decrease in arch length.
Tooth size→ The mesiodistal tooth size has been discussed as a
causative factor of the late crowding. Begg (1954) analyzed interproximal
attrition in old Australian aborigines and concluded that teeth in modern man
are too large for the dental arches and hence become crowded. Corrucini (1990)
showed that small jaws rather than large teeth underlie tooth-arch discrepancy.
………………..

Mandibular 3rd molars→ Richardson (1989) stressed that the third
molar plays a passive role in the development of late lower arch crowding.
Arch width changes→ Richardson (1995) showed that increased
lower arch crowding could be found in association with both increased and
decreased arch width, depending on the direction of movement of the
canines. Decrease of the mandibular intercanine width is generally
considered to be associated with late lower crowding.
Because dental development continues at a slow persistent rate from
adolescence into adulthood, there is no definitive method to distinguish
between normal age-related events and relapse after orthodontic treatment.


SOFT TISSUE MATRIX
-The dentoalveolar changes are not only the result of the influence of
growth on tooth movements but also a function of the soft tissue matrix
surrounding the hard tissue structures.
-It has been stressed that in the absence of muscular imbalance, a
well-established interdigitation may greatly assist in maintaining the end result
of tooth movement. Establishing the most precise intercuspal relationship
between dental arches will not prevent relapse from occurring if a strong
adverse muscular pressure exists.
-It is therefore important to stress that if a malocclusion, caused or
maintained by muscular or other soft tissue dysfunction, has been
morphologically corrected without any alteration in muscular behaviour, a
stable posttreatment result is unlikely.


TREATMENT TIME & PATIENT’S AGE
-Corrections carried out during periods of growth and eruption of
teeth is considered to be less likely to relapse.
-According to Reitan (1967), there will be little or no relapse following
orthodontic movement of an erupting tooth, because its supporting tissues are
in a stage proliferation as a result of the eruption process.
-New fibers will be formed as the root develops, and these new fibers
will assist in maintaining the new tooth position.


PERIODONTAL FORCE AND RELAPSE
Southard and Tolley (AJO 1992) investigated the interproximal force
(IPF) at the mandibular first molar-second premolar contact and determined
that whether the periodontium maintains the contacts of approximating
mandibular teeth in a continuous state of compression. Results indicated that,
-Contacts of approximating mandibular teeth are maintained in a
continuous state of compression. This compressive force is generated by the
supporting periodontium and acts through the dental contact points, even when
the dental arches are apart. Further, this force is increased for a period after
chewing.
…………………


-If inter proximal force (IPF) does exert an influence on dental
alignment, it probably acts in conjunction with lip and cheek forces to collapse
the arch and is opposed by tongue force, which tends to expand the arch. It
follows that the influence of IPF should be more evident in the anterior region
of the arch where the contact points are narrower, the crowns more tapered,
and the expansive force from the tongue more intermittent than in the
posterior region of the arch.
-The existence of a continuous, compressive force (IPF), originating
in the periodontium and acting on approximating teeth at their contact points,
which is increased after occlusal loading, may help to explain long-term post
treatment crowding of the mandibular anterior teeth, physiologic drifting of
teeth, and maintenance of posterior dental contacts after interproximal wear.


RETENTION AFTER CLASS II CORRECTION:


Relapse toward a Class II relationship must result from some
combination of tooth movement (forward in the upper arch, backward in the
lower arch, or both) and differential growth of the maxilla relative to the
mandible. In Class II treatment, it is important not to move the lower incisors
too far forward, but this can happen with Class II elastics. In this situation lip
pressure will tend to upright the protruding incisors, leading relatively quickly
to crowding and return of both overbite and overjet.
Overcorrection of the occlusal relationships as a finishing procedure is
an important step in controlling tooth movement that would lead to Class II
relapse. Even with good retention, 1 to 2 mm of anteroposterior change caused
by adjustments in tooth positions is likely to occur after active treatment stops.
As a general guideline, if more than 2 mm of forward repositioning of the
lower incisors occurred during treatment, permanent retention would be
required.
………………..

The slower long term relapse that occurs in some patients who did not have
inappropriate tooth movement results primarily form differential jaw growth.
This relapse tendency can be controlled in one of two ways:
- The first is to continue headgear to the upper molars on a reduced
basis (at night, for instance) in conjunction with a retainer to hold the teeth in
alignment. This is quite satisfactory in well motivated-patients who have been
wearing headgear during treatment and is compatible with traditional retainers
that are worn full-time initially.
………………….


- The second method is to use a functional appliance of the activatorbionator type to hold both tooth position and the occlusal relationship. If the
patient does not have excessive overjet at the end of active treatment, the
construction bite for the functional appliance is taken without any mandibular
advancement- the reason being to prevent a Class II malocclusion from
recurring. A potential difficulty is that the functional appliance will be worn
only part-time, typically just at night, and day time retainers of conventional
design also will be needed to control tooth position during the first few
months. For patients with less severe problems, in whom continued growth
may or may not cause relapse, it may be more rational to use only
conventional maxillary and mandibular retainers initially, and replace them
with a functional appliance to be worn at night if relapse is beginning to occur
after a few months.
This type of retention is often needed for 12 to 24 months or more in
patients with a severe skeletal problem initially. The guideline is: the more
severe the initial Class II problem and the younger the patient at the end of
active treatment, the more likely that either headgear or a functional appliance
will be needed as a retainer.

RETENTION AFTER CLASS III CORRECTION:


Relapse from continuing mandibular growth is very likely to occur and
such growth is extremely difficult to control. Applying a restraining force to
the mandible, as from a chincap tends to rotate the mandible downward,
causing growth to be expressed more vertically and less horizontally, and Class
III functional appliances have the same effect. If face height is normal or
excessive after orthodontic treatment and relapse occurs from mandibular
growth, surgical correction after the growth has expressed itself may be the
only answer. In mild Class III problems, a functional appliance or a positioner
may be enough to maintain the occlusal relationships during post treatment
growth.


RETENTION AFTER DEEP BITE CORRECTION:
In correcting excess overbite, the majority of patients require control of
vertical overlap of incisors during retention. This is accomplished most readily
by using a removable upper retainer combined with a bite plane so that the
lower incisors will encounter the baseplate of the retainer if they begin to slip
vertically behind the upper incisors. The retainer does not separate the posterior
teeth. As vertical growth continues into the late teens, the retainer often is
needed for several years after fixed appliance orthodontics is completed.


RETENTION AFTER ANTERIOR OPEN BITE
CORRECTION:


Relapse into anterior open bite can occur by any combination of
depression of the incisors and elongation of the molars. Active habits such as
thumbsucking and tongue-thrust swallowing are often blamed for relapse
into open bite, but the evidence to support this contention is not convincing.
In patients who do not place some object between the front teeth, return of
open bite is almost always the result of elongation of the posterior teeth,
particularly the upper molars without any evidence of intrusion of incisors.
Excessive vertical growth and eruption of posterior teeth often continue until
late in the teens or early twenties. Controlling eruption of the upper molars is
therefore the key to retention in open bite patients.

………………..


High pull head gear to the upper molars, in conjunction with a
standard removable retainer to maintain tooth position, is one effective way to
control open bite relapse. A better alternative is an appliance with bite blocks
between the posterior teeth (an open bite activator or bionator), which stretches
the patients soft tissues to provide a force opposing eruption. A patient with a
severe open bite problem is particularly likely to benefit from having
conventional maxillary and mandibular retainers for daytime wear, and an open
bite bionator as a nighttime retainer from the beginning of the retention period.


RETENTION OF LOWER INCISOR ALIGNMENT:
Continued skeletal growth can not only affect the occlusal
relationships, but also alter the position of the teeth. If the mandible grows
forward or rotates downward, the effect is to carry the lower incisors into the
lip, which creates a force tipping them distally. For this reason continued
mandibular growth in normal or Class III patients is strongly associated with
crowding of the lower incisors. Incisor crowding also accompanies the
downward and backward rotation of the mandible seen in open bite problems.
A retainer in the lower incisor region is needed to prevent crowding
from developing, until growth has declined into adult levels. It also has been
suggested that orthodontic retention should be continued, at least on a parttime basis, until the third molars have either erupted into normal occlusion or
have been removed.


LONG-TERM RETENTION STUDIES

…………….

TREATMENT MODALITIES
Several long-term retention studies evaluating the stability of different
treatment modalities have been reported. The main center for much of this
research is the University of Washington. Most of the research is centered on the
mandibular arch with the assumption that alignment of the lower arch serves as
a template around which the upper arch develops and functions.
Most of the studies report on the Irregularity index (Little R AJO 1975),
arch length, and intercanine width. It is important to note that the terms
crowding and arch length deficiency are not synonymous with the irregularity
index. The irregularity index measures displaced anatomic contact points of the
teeth and gives an objective value to subjective crowding of the case. Arch
length deficiency on the other hand represents the space needed for alignment
of teeth.


The following treatment modalities have been studied:
Late extraction followed by full treatment
Serial extraction without treatment
Serial extraction followed by appliance therapy
Non extraction therapy with expansion
Early mixed dentition treatment without fixed appliance therapy
Non extraction therapy with generalized spacing
Lower incisor extractions

LATE EXTRACTION FOLLOWED BY FULL TREATMENT
Little et al.(AJO 1981) reports on 65 first premolar extraction patients
at least 10 years postretention. Mandibular arch shortening was seen in 63 of
the 65 patients. The crowding posttreatment was not associated with the
degree of arch length reduction. Intercanine width change during the
treatment and the duration of retention were not predictive of postretention
crowding. The overall success rate, defined as an irregularity index of less
than 3.5 mm, was less than 30% with 20% showing marked crowding.
Shields et al.(AJO 1985) reevaluated 54 of the patients from the 1981
study and failed to find any clinically significant predictors or associations of
value between the dental-cast measurements and cephalometric data. Any
change in cephalometric parameters postretention failed to explain
postretention crowding.

SERIAL EXTRACTION WITHOUT TREATMENT
Kinne (University of Washington 1975) reported on 55 patients who
had undergone serial extraction without any appliance therapy. The patients,
examined at least 10 year after the extraction of premolars, showed an
increase in post treatment irregularity.
Persson et al. (EJO 1989) reported on 42 patients an average of 20
years after serial extraction therapy. Most of the cases showed redevelopment
of crowding, however, it was less pronounced than pretreatment and when
compared with untreated normals there was no difference in the crowding
evident between the two groups.


SERIAL EXTRACTION FOLLOWED BY APPLIANCE THERAPY
Anticipated future stability is one of the objectives of serial extraction
therapy. Tweed(1966) postulated that early self-alignment should result in
improved stability. Engst (University of Washington 1977) studied 30 patients
at 5 years postretention, and Little et al. (AO 1990) reported on the same
sample at least 10 years postretention. Clinically unsatisfactory mandibular
anterior alignment occurred in 73% of the cases and decreases in intercanine
width and arch length was found in 29 of the 30 cases.
McReynolds and Little (AO 1991) found no difference in postretention
irregularity between first and second premolar extraction cases. Both the first
and second premolar extraction cases showed a reduction in arch length and
width and were unpredictable relative to long-term alignment. When
compared to the late premolar extraction group, the success rate of less than
30% was no different.


NONEXTRACTION THERAPY WITH EXPANSION
Twenty-six patients who had at least 1 mm of arch development
during the mixed dentition were studied at least 6 years postretention (Stein
UoW 1974 & Little AJO 1990). All the patients showed a reduction in arch
length after treatment and only five patients maintained an overall increase of 1
mm.
Moussa et al. (AJO 1995) reported on a sample of 55 patients who had
undergone rapid palatal expansion in conjunction with edgewise
mechanotherapy a minimum of 8 years postretention. Their results showed
good stability for upper intercanine, upper and lower intermolar widths, and
lower incisor irregularity. Stability of the mandibular intercanine width,
however, was poor with the posttreatment position closely approximating the
pretreatment dimension.
………………..

The stability of nonextraction treatment with prolonged retention was
studied by Sadowsky et al., (AJO 1994) who looked at 22 patients an average of
8.4 years postretention (minimum, 5 years). The mandibular incisor irregularity
increased during the postretention period but at 2.4 mm was still in the
acceptable range.
Elms et al. (AJO 1996) recently reported on a sample of 42 patients
with Class II Division I malocclusion, who were treated without extraction and
with headgear and fixed appliances. Final records were taken an average of 6.5
years postretention (minimum, 3 years). Some incisor reproximation was
preformed on removal of the mandibular bonded retainer. Ninety percent of
the sample had incisor irregularity of less than 3.5 mm postretention. They
conclude that the factors responsible for the stability seen are the application
of proper mechanics, a cooperative patient, and favorable downward and
forward mandibular growth.

The above cases showed only minimal crowding pretreatment

EARLY MIXED DENTITION TREATMENT WITHOUT FIXED
APPLIANCE THERAPY
Dugoni et al.(AO 1995) reported on the postretention stability of cases
who had early mixed dentition treatment followed by the placement of a
mandibular bonded retainer. No appliance therapy was carried out in the
permanent dentition. Circumferential supracrestal fiberotomy or interproximal
enamel reduction was carried on removal of the bonded retainers. The
irregularity index in this sample at the postretention stage showed satisfactory
mandibular incisor alignment in 76% of the cases. In contrast to other studies,
maintenance of postretention intermolar width was also noted. It is suggested
that the early establishment of an intermolar width and improved occlusion in
the mixed dentition provides better long-term stability.


NONEXTRACTION THERAPY WITH GENERALIZED SPACING
Thirty patients with mandibular spacing pretreatment were studied
10 years postretention (Little AJO 1989). Of all the treatment modalities
studied, this treatment displayed the most long-term stability with an
irregularity index value of 3.38 mm. This was still slightly higher, however,
than the value of 2.7 mm for untreated norms. Minimal relapse of overjet and
overbite was evident. Some intercanine width reduction was evident in most
cases. The overall success rate in this group was 50% postretention.
Mandibular spaces did not reopen in any case. However, the maxillary arch
showed more variation; the midline diastema was the most common areas of
space recurrence.


LOWER INCISOR EXTRACTIONS
Riedel (JCO 1976) observed an increase in post treatment stability after
an informal review of patients who had two mandibular incisors removed. He
then carried out a long-term study to specifically determine the stability and
relapse of the mandibular incisor extraction therapy (AO 1992). Twenty-four
patients who had a single mandibular extraction followed 6.5 years
postretention and 18 patients with two mandibular incisor extractions followed
for a period of 9.75 years were studied. Twenty-nine percent of the single incisor
extraction group and 56% of the two incisor extraction group demonstrated
unacceptable mandibular incisor alignment at the postretention stage. This
compares favorably to the results of previously reported premolar extraction
cases.


…………SUMMARY OF POSTTREATMENT CHANGES:
Intercanine width reduction is seen posttreatment whether the case
was expanded during treatment or not.
The intermolar width tends to return to the pretreatment value during
the postretention period in most of the studies. These reported changes in
intercanine and intermolar width are greater in the mandibular arch than the
maxillary arch.
Although most of the arch changes are seen before age 30, mandibular
anterior crowding continues into the fifth decade.
As summarized by Little et al. “treated cases should be viewed as
dynamic and constantly changing, at least through the third and fourth decade
and perhaps throughout life.”
Of all the treatment modalities studied only three showed acceptable
long-term mandibular incisor alignment postretention. These were the early
mixed dentition treatment with no fixed appliance therapy, the nonextraction
therapy with generalized spaces, and the lower incisor extraction cases.

ORTHOGNATHIC SURGERY
MAXILLARY SURGERIES

Schuchardt (1959) first reported superior movement of the maxilla, who used a twostage approach and limited his surgical procedure to the posterior maxilla. He
reported relapse problems that in retrospect probably were caused primarily by
incomplete mobilization of the dentoalveolar segments at surgery.
Willmar (1974) undertook the first quantitative follow-up study on LeFort I
osteotomy with the use of surgically placed metal markers. Although 106 patients
were studied, only three had ''idiopathic long face.'' These cases demonstrated
stability of markers and occlusion throughout the 1-year observation period, with an
''insignificant" 10% superior relapse occurring at the anterior marker.
Bell and McBride (1977) examined 41 patients with vertical maxillary excess who
underwent maxillary superior repositioning by LeFort I osteotomy. They evaluated
their results clinically and noticed stability without relapse in the cases examined.
Hartog (1982) evaluated skeletal stability and soft-tissue changes after superior
repositioning of the maxilla, and reported that good stability was attained. The
sample included multiple segments and combined procedures with only three onepiece osteotomies.
Washburn, Schendel, and Epker (1982) reported their experiences with superior
maxillary repositioning in a group of 15 young patients and indicated that the
postsurgical jaw relationship was maintained even in patients who experienced
postsurgical growth.

MANDIBULAR

SURGERIES

Lake, McNeill, Little (AJO 1981) evaluated surgical advancement of the mandible by
retrospective cephalometric and computer analysis for longitudinal skeletal and
dental changes an average of 3½ years after surgery. 52 patients (19 males and 33
females) underwent surgical advancement of the mandible by means of bilateral
sagittal osteotomy of the mandibular vertical rami.
From the results, relationships between specific parameters and skeletal relapse have
been demonstrated:
-Positional change of the proximal segment was found to be the most important
parameter in determining stability or relapse of the advanced mandible.
-Anteroinferior condylar displacement and increase in posterior facial height at the
time of surgery or immediately postoperatively were associated with subsequent
skeletal relapse of the distal mandibular segment.
-The magnitude of advancement was a primary factor in mandibular stability. As the
magnitude of advancement increased, the net amount of relapse tended to increase.
-The dynamic function and variability of the mandible's musculoskeletal system and
its periosteal integument may play a dominant role in the nature of the postsurgical
response.
-Preoperative measurement of the mandibular plane angle did not prove to be a
reliable predictor of subsequent mandibular relapse. However, patients with high
mandibular plane angles did undergo more relapse than did patients with either
normal or low angles.
-No significant relationship was found between skeletal relapse and the age of the
www.indiandentalacademy.com ………………….
patient.

Huang and Ross (AJO 1982) evaluated the short-term and long-term effects of
surgical lengthening of the retrognathic, growing mandible in children.
Twenty-two patients 12 boys and 10 girls underwent mandible-lengthening
procedures at the mean ages of 14.1 years (boys) and 13.4 years (girls).
The results indicated that,
-The response to this mandible-lengthening surgery in the growing child
varied with the amount of lengthening performed but did not appear to vary
with age (after 11 years), sex, etiology of the mandibular discrepancy,
mandibular plane angle, deep- or open-bite, or concomitant surgical
procedures.
-Lengthening of more than 11 mm. was usually accompanied by extensive
relapse, with major remodeling of the condyle or posterior symphysis or both.
Lengthening of less than 9 mm. was followed by little or no relapse.
-No further clinically significant growth of the mandible occurred following
mandible lengthening as performed after the age of 11 years.
-The mandible returned to its preoperative growth direction within 2 years
after surgery.

FUNCTIONAL APPLIANCE TREATMENT
Pancherz (AJO 1991) performed a long term cephalometric investigation to analyze the
nature of Class II relapse after Herbst appliance treatment, comparing stable and
relapse cases at least 5 years after treatment. A total of 118 patients with Class II,
Division 1 malocclusions were treated with the Herbst appliance. Lateral cephalograms
taken before and immediately after Herbst treatment, as well as 6 months and 5 to 10
years after treatment, were analyzed.
The results revealed that,
-Relapse in the overjet and sagittal molar relationship resulted mainly from
posttreatment maxillary and mandibular dental changes.
-In particular, the maxillary incisors and molars moved significantly to a more anterior
position in the relapse group than in the stable group.
-The interrelation between maxillary and mandibular posttreatment growth was
favorable and did not contribute to the occlusal relapse.
-It is hypothesized that the main causes of the Class II relapse in patients treated with
the Herbst appliance were a persisting lip-tongue dysfunction habit and an unstable
cuspal interdigitation after treatment.
……………………..

Wieslander (AJO 1993) investigated the long-term effect of treatment with headgearHerbst appliance in early mixed dentition in children with severe Class II
malocclusions. A group of children age 8 years 8 months was initially treated for 5
months with a headgear-Herbst appliance followed by a 3- to 5-year period of
activator retention. The patients were studied out of retention at the mean age of 17
years 4 months and compared with an untreated control group.
Positive findings of the study includes the following:
-A rapid improvement of the anteroposterior jaw discrepancy because of 24-hour wear
of the appliance for 5 months.
-A significant maxillary effect during active treatment and retention resulting in a 2.3
mm posterior gain after retention, which compensates for the mandibular relapse
tendency. It resulted in an average statistically and clinically significant 2.9° reduction
of the ANB angle and a 3.8 mm skeletal improvement of the sagittal jaw relationship
out of retention.
Negative findings include the following:
-A prolonged retention ranging over several years of activator wear was necessary to
minimize relapse after Herbst treatment.
-A modest long-term effect on the mandible 8 years after treatment. In many cases the
long-term mandibular effect was considerably larger and of clinical importance.
However, in other cases that cooperated poorly during retention, it was less.
-A rather small increase in mandibular length. The significant average 2.0 mm
increase in the condylion-gnathion distance observed after 5 months of Herbst
treatment was reduced to 1.2 mm after retention and was not statistically significant.

RETENTION PLANNING
Retention Planning is divided into three categories, depending
on the type of treatment instituted:
(1) limited retention
(2) moderate retention ( in terms of both time and appliance
wearing)
(3) permanent or semi permanent retention


CONDITIONS WHERE LIMITED RETENTION IS REQUIRED:
(a) Corrected Crossbites
-Anterior: when adequate overbite has been established
-Posterior: when axial inclinations of posterior teeth remain reasonable
after corrective procedures have been completed
(b) Dentitions that have been treated by serial extraction
-High canine extraction cases
-Cases calling for extraction of one or more teeth
(c) Corrections that have been achieved by retardation of maxillary growth ,
whether dental or skeletal, after the patient has passed through the growth
period
(d) Dentitions in which the maxillary and mandibular teeth have been
separated to allow for eruption of teeth previously blocked out.

CONDITIONS WHERE MODERATE RETENTION IS REQUIRED:
(a) Class I non extraction cases, characterized by protrusion and
spacing of maxillary incisors. These require retention until normal lip and
tongue function has been achieved.
(b) Class I or Class II extraction cases probably require that the teeth
be held in contact, particularly in the maxillary arch, until lip and tongue
function can achieve a satisfactory balance. It is generally desirable to use a
maxillary Hawley type of retainer until normal functional adaptation has
occurred. It is sometimes also desirable to use either a maxillary Kloehn-type
headgear, whose force is directed to the permanent first molars, or a
labiobuccal type of appliance, with cervical or occipital resistance applied at
night.
……………….

(c) Corrected deep overbites in either Class I or Class II malocclusions
usually require retention in a vertical plane.
-if anterior teeth were depressed to achieve overbite correction, a
bite plane on a maxillary retainer is desirable. To be effective in retaining
overbite correction, the bite plane should be worn continuously for perhaps the
first 4 to 6 months, including while the patient is eating. In deep overbite
cases overcorrection is usually desirable and equilibration and adjustment to
functional occlusion is necessary.
-If overbite correction was achieved as a result of bite opening and
mandible was forced away from the maxilla, vertical dimensions should be
held until growth (ie, mandibular ramal height) can catch up.
-Severe occlusal plane tipping may also require extended retention
protocols and possibly additional maxillary restraint as well.
……………….

(d) Early correction of rotated teeth to their normal positions .
-Perhaps before root formation has been completed
-In the mandibular incisor area a removable type of appliance with
a labial bow is probably best. In this area, the occlusal splint type retainer or
cast lower partial, as suggested by Lande, may be useful.
(e) Cases involving ectopic eruption of teeth or the presence of
supernumerary teeth require varying retention times, usually prolonged, and
occasionally a fixed or permanent retentive device.
(f) The corrected Class II div 2 malocclusion generally requires
extended retention to allow for the adaptation of musculature.


CONDITIONS WHERE PERMANENT OR SEMI PERMANENT
RETENTION IS REQUIRED:
(a) Cases in which expansion has been the choice of treatment,
particularly in the mandibular arch, may require either permanent or
semipermanent retention to maintain normal contact alignment.
(b) Cases of considerable or generalized spacing may require
permanent retention after space closure has been completed.
(c) Instances of severe rotation or severe labiolingual malposition may
require permanent retention, as provided by bonded retainers.
(d) Spacing between maxillary central incisors (diastema) in otherwise
normal occlusions sometimes require permanent retention, particularly in
adult dentitions.


TIMING OF RETENTION: SUMMARY
Retention is needed for all patients who had fixed orthodontic
appliance to correct intra-arch irregularities. It should be:
Essentially full time for the first 3 to 4 months, except that the retainers

not
only can but should be removed while eating (unless circumstances
like periodontal bone loss require permanent splinting).

Continued on a part time basis for at least 12 months, to

remodeling of gingival tissues.

allow time for

If significant growth remains, continued part time until completion of

growth.

This would mean that nearly all patients treated in the early
permanent dentition will require retention of incisor alignment until the late
teens, and in those with skeletal disproportions initially, part time use of a
functional appliance or extra oral force probably will be needed.

RETENTION APPLIANCES
Requirements of Retaining Appliances:
1. It should restrain each tooth that has been moved into the desired
position in directions where there are tendencies towards recurring
movements.
2. It should permit the forces associated with functional activity to act
freely on the retained teeth, permitting them to respond in as nearly a
physiologic manner as possible.
3. It should be as self-cleansing as possible and should be reasonably
easy to maintain in optimal hygienic condition.
4. It should be constructed in such a manner as to be as inconspicious as
possible, yet should be strong enough to achieve its objective over the
required period of use.

RETAINER DESIGN
Removable retainers

with a labial bow (Hawley, Begg and Barrer type
retainers):

Removable Appliances can serve effectively for retention against
intra-arch instability and are also useful as retainers (in the form of modified
functional appliances or part-time headgear) in patients with growth
problems. These retainers are robust and can be worn during eating. Hawley
retainers have been recently shown to have the advantage of facilitating
posterior occlusal settling in the initial three months of retention (Sauget E,
AO 1997). The labial bow can be used to accomplish simple tooth movements
if required, and an anterior biteplane can easily be incorporated for retention
of a corrected deep overbite.


HAWLEY

WRAP AROUND

BARRER



Removable vacuum formed retainers (Transparent Plastic
Invisible Retainers):
Vacuum formed retainers are relatively inexpensive and can be quickly
fabricated on the same day as appliance removal. They are discreet and can
be modified to produce tooth movements if required. Full posterior occlusal
coverage (including second molars if present) is advisable in order to reduce
the risk of overeruption of these teeth during retention.
The Essix retainer is an example of the invisible retainer that only
incorporates the six anterior teeth of each arch. These appliances allow for the
settling of the posterior teeth into better occlusion. Due to their inherent
flexibility, however, they cannot be used to retain cases in which arches have
been expanded during orthodontic treatment.
Recent research has shown that vacuum formed retainers were
significantly less effective in promoting posterior occlusal settling than
Hawley retainers (Sauget E, AO 1997). However this is likely to be of little
importance if good posterior intercuspation has been established by the time
of debonding.

ESSIX THERMOPLASTIC COPOLYESTER
RETAINERS




Fixed bonded retainers (Smooth wire, Flexible Spiral wire):
Fixed retainers are indicated for long-term retention of the labial
segments, particularly when there is reduced periodontal support, and for
retention of a midline diastema (Proffit). Fixed retainers are discreet and
reduce the demands on patient compliance. However they are associated
with failure rates of up to 47% (Bearn DR, AJO 1995), particularly on
upper incisors when there is a deep overbite. In addition, calculus and
plaque deposition is greater than with removable retainers. Fixed
retainers therefore require long term maintenance.

There are four major indications:
1) Maintenance of lower incisor position during late growth
2) Diastema maintenance
3) Maintenance of pontic or implant space
4) Keeping extraction space closed in adults
Flexible spiral wire retainers allow differential tooth movement and
are particularly useful for patients with loss of periodontal support.
Current orthodontic opinion recommends either the use of 0.0215 inch
multistrand wire, (Heier EE, AJO 1997) or 0.030 - 0.032 inch sandblasted
round stainless steel wire (Zachrisson JCO 1995).



Active Retainers:
Relapse or growth changes after orthodontic treatment will lead to
a need for some tooth movement during retention. This usually is
accomplished with a removable appliance that continues as a retainer
after it has repositioned the teeth.

It usually used in two specific situations:
•
Realignment of Irregular Incisors (Spring Retainers), and as
•
Functional appliances to manage Class II or Class III relapse
tendencies.

SPRING RETAINER




Positioners:

Positioners are elastomeric or rubber removable retainers that are
either preformed or custom made. Preformed positioners are available for
bicuspid extraction cases and non-extraction cases. Sizes are determined by
measuring the mesiodistal dimensions of the six anterior teeth. These
preformed positioners cannot compensate for individual variation in the size of
the teeth, arch width, arch form or tooth size discrepancies. For these reasons,
they should only be used temporarily.
Custom-made positioners are fabricated on articulated models in
which teeth from both arches have been sectioned from the models, realigned
and waxed in an ideal configuration. This incorporates minor corrections in
tooth position and occlusal relationship. The elastomeric or rubber material is
then formed around the teeth and the coronal portion of the gingiva.

POSITIONERS


RECOVERY AFTER RELAPSE
Despite the utmost care in Treatment and Retention, if Relapse occurs the
following can be considered:
1)

Retreatment may take the form of rebanding or rebonding most if not all
teeth. It is sometimes expedient to consider the removal of certain teeth,
particularly if the relapse occurs in the form of crowding. In any case
attempt should be made to discover and eliminate factors that appear
contributory to relapse.

2)

The mandibular lingual arch helps to realign the teeth in instances of
mandibular collapse or crowding. Light pressure against mandibular
anterior teeth may be used to realign them.

3)

Springs and clasps can be added to maxillary Hawley retainer to assist in
repositioning and control of labiolingual deviations.

4)

Spring retainers using both facial and lingual acrylic for added leverage and
labial bows for increased flexibility may be used for minor realignment.
Teeth are sectioned and aligned on the retainer model and active retainer is
fabricated to the realigned relationship. Interproximal stripping is
sometimes beneficial.

5) The maxillary labiobuccal retainer, Kloehn-type headgear, or functional
appliances may be used against the maxillary arch to provide recorrection
in instances of relapse toward a Class II relationship.
6) Habit training in the form of tongue and lip therapy may be beneficial
when abnormal habit patterns have caused orthodontic relapses.
Removable appliances are also helpful as tongue restraints.
7) Equilibration and trimming may be all that is necessary to achieve esthetic
and functional satisfaction for the patient and orthodontist.
8) In certain cases it may be desirable to suggest that the patient accept
minimal relapses rather than continue with prolonged treatment or
retention.


CONCLUSION
Maintaining the treatment result following orthodontic
treatment is one of the most difficult aspects of the entire
treatment process. Normal maturational changes, together
with post-treatment tooth alterations, conspire against longterm stability. All treated malocclusions must eventually be
returned from control by appliances to control by the patient’s
own musculature. Permanent retention is increasingly being
recommended as the only way to ensure long-term stability of
an orthodontic treatment result. Proper goals of treatment,
careful mechanotherapy, precise occlusal equilibration, and
well-chosen retention procedures play a role in achieving
occlusal homeostasis.

Thank you
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